feat(remote): 实现文件下载真实进度显示

- 下载改用流式读取，计算真实进度百分比
- 通过 IPC 事件实时推送进度到前端
- 支持 Content-Length 计算下载进度

src/modules/remote/api.ts

@@ -119,13 +119,31 @@ export const downloadFileFromRemote = async (
   password?: string,
   onProgress?: (progress: number) => void
 ): Promise<void> => {
-  onProgress?.(50)
-  const result = await window.electronAPI.remoteDownloadFile(serverHost, port, fileName, remotePath, localPath, password)
-  onProgress?.(100)
-  if (!result.success) {
-    if (result.canceled) {
-      return
+  const transferId = Date.now().toString()
+
+  const cleanup = window.electronAPI?.onDownloadProgress?.((data) => {
+    if (data.id === transferId) {
+      onProgress?.(data.progress)
     }
-    throw new Error(result.error || 'Download failed')
+  })
+
+  try {
+    const result = await window.electronAPI.remoteDownloadFile(
+      transferId,
+      serverHost,
+      port,
+      fileName,
+      remotePath,
+      localPath,
+      password
+    )
+    if (!result.success) {
+      if (result.canceled) {
+        return
+      }
+      throw new Error(result.error || 'Download failed')
+    }
+  } finally {
+    cleanup?.()
   }
 }